The shuttling diffusion of polysulfides is a bottleneck that seriously limits the performance of Li-S batteries.Purposeful construction of sulfur cathodes with reliable trapping ability of polysulfides is the key to overcome such limitation.Herein,a hierarchical porous architecture,i.e.,Co(OH)_(2)sheets bonded Ti_3C_(2)T_x MXene aerogel(Co(OH)_(2)/MXA),is constructed via a facile selfassembled approach and used as an efficient free-standing polysulfides reservoir.The interconnected three-dimensional(3D)porous network with void space and strong interfacial interaction not only enables high sulfur loading but facilitates fast ion and electron transport.Experimental and theoretical results confirm the hetero-framework exhibits outstanding immobilization and conversion ability for polysulfides due to its polar surface and bifunctional catalytic activities toward both formation and decomposition of Li2S.The optimized Co(OH)_(2)/MXA cathode delivers excellent rate capability(407 mAh·g^(-1)at 5C)with a sulfur loading of 2.7 mg·cm^(-2),and ultra-stable cycling performance as an extremely small capacity decay of~0.005%per cycle within 1700 cycles at 1C is achieved with a high sulfur loading of 6.7 mg·cm^(-2).More significantly,our design structural/componential methodology here promises the MXene-based aerogel electrodes for LiS batteries and beyond.
Yang LiuKe TanSen LiuXu ZhangMao-Qiang ShenXue-Sen LiuXin-Yue GaoLin-Rui HouChang-Zhou Yuan
CeO_(2)plays an important role in heterogeneous catalysis,and its performance is highly dependent on the oxygen vacancies and surface defects,which can be easily tuned by manipulating the particle dimensions and morphology.In this article,we report a facile strategy to synthesize a new type of CeO_(2)with modified surface property which can improve its ability to active oxygen.The obtained ball-type 3D selfassemble CeO_(2)(M-CeO_(2)) is composed of large amounts of small 1D crystals which are stro ngly connected with each other.Detailed characterizations confirm its morphology,particle size and improved reducibility with abundant fraction of Ce^(3+)and more surface active oxygen when compared with CeO_(2)-nanorods and CeO_(2)-nanocubes.In the catalytic wet air oxidation(CWAO)of N,N-dimethylfo rmamide,the total organic carbon(TOC)and total nitrogen(TN)conversion of M-CeO_(2)at 180℃in 3 h are 68%and 46%,respectively,which are higher than that of CeO_(2)-nanorods and CeO_(2)-nanocubes.Besides,M-CeO_(2) presents the lowest activation energy,which is related to its modified surface property.The good stability with consecutive four reactions of M-CeO_(2)in catalytic reactions suggests its potential application in CWAO processes for industrial wastewater treatment.
Using the idea of material design and the design of reaction system and conditions,quasi-one-dimensional nano-materials with ribbon-like structure were successfully prepared.Nickel tartrate nanobelts were prepared by a sol-precipitation route,using nickel chloride hexahydrate and tartaric acid as raw materials,and using ammonium hydroxide as pH value modifier.Nickel nanobelts with smooth surface were prepared by a thermal-decomposition route at about 355℃for about 30 minutes,in CO_(2) atmosphere,using nickel tartrate nanobelts as precursor.The analyses of atomic absorption spectrometry(AAS),organic elemental analyzer(OEA),infrared spectroscopy(IR)and ultraviolet-visible spectroscopy(UV-Vis)indicate that the products as-prepared is nickel tartrate,which has octahedral configuration of co-ordination of nickel atoms.The images of scanning electron microscopy(SEM)indicate that the morphology of nickel tartrate as-prepared is an obvious belt structure with clear and smooth surface.The images of SEM also indicate that the nickel nanobelts have clear and smooth surface.The nickel nanobelts are about tens of micrometers in length,tens of nanometers in thickness,and 100-200 nanometers in width.
It is well-known that amphiphilic star-shaped copolymers can self-assemble in selective solvents to form complicated micellar constructs as a synergistic result of both the topological constraints and relative volume fractions of the arms.Although the association phenomena of amphiphilic stars have been observed in nonselective solvents,both the structural detail and formation mechanism of these associates are not clear yet.Moreover,these experimental observations are controversial with respect to molecularly dispersed starlike copolymers in nonselective solvents as is popularly believed.To clarify these issues,we have synthesized a series of polyoxometalate-based polystyrene-poly(ethylene glycol)(PS-PEG)miktoarm star supramolecular copolymers(SEW-1–5)by coupling a Keggin-type polyoxometalate of K4[α-SiW12O40]with 1,2,3-triazolium bridged block copolymers of-PSn-b+-PEGmI-(n=17,26,39,57,81;m=45)through ionic exchange reactions,respectively.TEM imaging,contact angle and 1H NMR studies reveal that SEW-2–5 self-assemble in chloroform,THF,and toluene to create micellelike aggregates ranging from cylinder to sphere with a PS corona and a PEG core,while for SEW-1,reverse bilayers are captured with a PEG corona and a PS core.Among these aggregates,the Keggin clusters of[α-SiW12O40]4-localize at the core-corona interfaces between PS and PEG.In terms of solvent quality,chloroform,THF,and toluene are only slightly poorer for PEG than that for PS with a relative order of chloroformself-assemble in co
Jie XiaoQun HeShengchao QiuHaoquan LiBinghua WangBin ZhangWeifeng Bu
A new Cu(Ⅰ)coordination polymer,[Cu4(MA)2(HCA)2]n(1,MA=melamine,H3CA=cyanuric acid),has been synthesized under hydrothermal conditions using CuCl2·2H2O and MA as the starting materials.Interestingly,cyanuric acid was obtained by the in situ hydrolysis and the deaminization of melamine,and the Cu(Ⅰ)ion was obtained by the in situ reduction of Cu(Ⅱ)ion during the self-assembly process.The crystal structure is of monoclinic,space group Pc with a=3.539(3),b=22.377(2),c=15.844(1)?,β=90.723(1)o,V=1254.6(2)?3,C12H14Cu4N18O6,Mr=760.61,Z=2,Dc=2.013 g/cm3,F(000)=752,μ=3.426 mm-1,R=0.0479 and wR=0.1243 for 3172 observed reflections(I>2s(I)).The crystal structural analysis revealed that the cooperation of coordinate-covalent bonds,intermolecular hydrogen bonds andπ-πinteractions give rise to a 3D supramolecular framework with 5-connected BN topology.Moreover,the thermal stability and luminescent property of 1 were also investigated.
The unique feather-like arrays composing of ultrathin secondary nanowires are fabricated on nickel foam(NF)through a facile hydrothermal strategy.Thus,the enhancement of electrochemical properties especially the low charge transfer resistance strongly depends on more active sites and porosity of the morphology.Benefiting from the unique structure,the optimized NiCo2O4 electrode delivers a significantly lower charge transfer resistance of 0.32Ω and a high specific capacitance of450 Fg^-1 at 0.5 A.g^-1,as well as a superior cycling stability of 139.6%capacitance retention.The improvement of the electrochemical energy storage property proves the potential of the fabrication of various binary metal oxide electrodes for applications in the electrochemical energy field.
